clamps argument of toExponential between 0 and 20 (#6423)

Author: veggiesaurus

src/core/core.ticks.js

@@ -49,7 +49,9 @@ module.exports = {
 				var maxTick = Math.max(Math.abs(ticks[0]), Math.abs(ticks[ticks.length - 1]));
 				if (maxTick < 1e-4) { // all ticks are small numbers; use scientific notation
 					var logTick = helpers.log10(Math.abs(tickValue));
-					tickString = tickValue.toExponential(Math.floor(logTick) - Math.floor(logDelta));
+					var numExponential = Math.floor(logTick) - Math.floor(logDelta);
+					numExponential = Math.max(Math.min(numExponential, 20), 0);
+					tickString = tickValue.toExponential(numExponential);
 				} else {
 					var numDecimal = -1 * Math.floor(logDelta);
 					numDecimal = Math.max(Math.min(numDecimal, 20), 0); // toFixed has a max of 20 decimal places